Snap action mechanism



Filed Jan. 12, 1946 FIG. 4

l N VEN TOR. 4/ aw/4 L BY Patented May 30, 1950 SNAP ACTION MECHANISM Oscar H.

, Sycamore, Ill., assignor to Kaminky First Industrial Corporation, Wilmington, Del.. a corporation of Delaware Application January 12, 1946, Serial No. 640,724 6 Claims. (Cl. 260-67) My invention relates to an improved snap action mechanism which, for instance, may be used in a precision type snap acting switch for making and breaking electrical circuits. By referring to the switch of my invention as being of the precision type, I mean one which operates in response to a very slight movement of an operating plunger, and one which is intended to operate consistently at the sa'me position of the plunger.

One commercial construction of my improved switch, for example, operates in response to a plunger movement in the order of a few ten thousandths of an inch between On" and Oil? positions with only a few ounces of operating force although controlling directly alternating current loads of a thousand watts or more.

An important object of my invention is the provision of a highly dependable precision type snap acting switch that may be manufactured in large quantities and assembled by unskilled labor rapidly and at low cost.

Other objects and advantages of my invention will appear from the following description and the accompanying drawings, in which:

Figure 1 is a top outside view of a single pole double throw switch illustrating one embodiment of my invention;

Fig. 2 is a sectional side view taken on the line 2-2 of Figure 1;

Fig. 3 shows a modification of the actuating means, and

Fig. 4 is a sectional view taken on the line 4-4 of Fig. 2.

Like reference characters refer throughout the drawing.

In the drawing the switch mechanism is mounted within the housing, generally designated 2|, and comprises a base portion or body 22 and a cover plate 23 secured to the base portion by suitable means (not shown). A rigid imperforate compression element or link 24 is formed with first and second oppositely extending pivot points designated 26 and 21, respectively, the first of these pivot points or edges being pivotally enmed by the housing boss 23 within the groove 23. The movable terminal member or actuator arm II is made of beryllium copper or some other resilient spring material and carries a third pivot point 32 at its free end. A U- or C-shaped tento like parts sion member 33, similarly made of beryllium copper or like spring material, and carrying the movable contact 34 between the stationary termithe pivot point 32 on the imperforate actuator arm 3|, and the notch 33 is pivotally engaged with the pivot point 21 on the link 24. The tension member 33, is formed with a bias or permanent set tending to contract it, that is, to urge the first and second notches to positions closer to one another than the position shown; thus when positioned as shown, the tension member 33 will be stressed in tension, the compression element 24 will be stressed in compression, and the first, second and .third pivot points will be forcibly and pivotally engaged with groove 29, notch 33 and notch 38, respectively.

The switch mechanism has two stable positions as shown in Figs. 2 and 3 where the third pivot point is out of alignment with the first and second pivot points; that is, the pivot point 32 ison one side or the other of a line drawn through the pivot points 26 and 21 on the link 24.

An important part of my invention resides in the way I mount the terminal members 3i, 33 and 31 by molding them integrally with the housing. Thus, assembly of the switch mechanism is carried out in a very simple manner, by moving the free end of terminal 3| sufficiently and to drop the plunger 4! in place, fitting the link 24 and the tension member 33 into their respective positions, and attaching the cover in any suitable way. With this construction a high production rate may be attained even with relatively unskilled labor.

The position of the parts shown in Fig. 2 is the normal position of the switch mechanism, the

movable contact 34 being disposed in engagement with the stationary contact or terminal 31 to conmeet it with terminal 3| through the tension element 33. When the operating means or plunger 4| is depressed, the flexible terminal or actuating arm 3| is moved from the position of Fig. 2 to the position of Fig. 3, during which movement the pivot point 32 is moved, against the force exerted by tension element 33, through the axis of maximum stress A-A in which pivot points 26,21 and 32 are aligned; after the pivot 32 passes through this position of maximum stress the tension member 33 moves by snap action to the position shown in Fig. 3 where terminal members 3| and 36 are connected through the tension member 33. Similarly, when the depressive force on the plunger is released, the resilient actuating arm 3| (which has been biased or permanently set to seek the position shown in Fig. 2) will move the pivot point 32 in the opposite direction against the force exerted by the tension element, through the axis B -B where the three points are again aligned: and from this axis 3-3 the tension member will-move by snap action to reassume the normal position shown in Fig. 2.

Directing attention more particularly now to the combined terminal member and actuating arm 3|, the switch is made self-returning to the Fig. 2 position by forming the actuator arm with a permanent set Just sufficient for it to overcome the tension set up by the stress in the tension member to cause it to return to its Fig. 2 position when the depressive force on the plunger is released; it will be obvious that the arm 3| may be biased in the opposite direction to be selfreturning to the Fig. 3 position instead,'in which case suitable plunger means will be provided to move the arm 3| to the Fig. 2 position. One method whereby the switch may be made nonreturning is by providing a tension member similar to tension member 33 but having sufflcient strength that the actuator arm 3| cannot move the pivot point 32 through the axis of maximum stress without the assistance of an outside force; another, obvious, method would be by providing the actuator arm with a pivot point (not shown) within the casing 2| instead of the flexible cantilever mounting illustrated in the figures; it will also be obvious that in so adapting the switch mechanism to non-returning operation a second plunger or operating means would preferably be provided in order to appl an operating force to the actuating arm in both directions.

A still further modification of my invention would be to form the actuator arm 3| of a thermally distortable bimetallic strip of the type conventionally employed in temperature responsive devices as shown in Fig. 3 whereby the switch may be responsive either to a condition transmitted through the plunger 4| or responsive to'ambient temperature or electrical overloads causing temperature rise in the arm.

While I have thus described a number of specific embodiments of my invention I am aware that numerous alterations and changes may be made therein without materially departing from the-spirit of the invention and the scope of the appended claims.

I claim:

1. In a snap acting device. a rigid imperforate link having first and second pivots at the ends thereof, stationary means for mounting said first pivot. an imperforate cantilever mounted resilient actuating means spaced directly below said link and in opposed face to face relation therewith, said actuatin means having a third pivot associated therewith. said second and third pivots being disposed on opposite sides of said first pivot. a resilient tension member spaced directly above said link and said actuatin means and in face to face relation therewith and extending arcuately around said first pivot. said tension memger having end portions movable between preselected positions and a central portion movab e between opposed positions on one side of said first pivot. said end portions pivotally engaging said second and third pivots. respectively, said link, actuating means and tension member forming a spring system having an axis of maximum stress defined by alinement of said pivots. said actuating means being biased to maintain said pivots slightly out of alinement in a preselected direction. and plunger means engageable with said actuating means for moving the end portion of the tension member associated with the third pivot through the axis of maximum stress to move ciated with the second pivot between its presclected positions with a snap action.

2. In an electric snap switch, a stationary contact, a relatively short rigid imperforate link having relatively broad sides and narrow edges and having first and second pivots, stationary means for mounting said first pivot, imperforate thermally distortable actuating means having relatively broad sides and narrow edges and disposed with one of its broad sides in face to face relation with one of the broad sides of said link, said actuating means having a third pivot. said first pivot being disposed between said second and third pivots, an elongated resilient tension member having relatively broad sides and narrow edges disposed with one of its broad sides in spaced face to face relation with the opposite broad side of said link extending arcuately around said first pivot, said tension member having end portions movable between preselected positions and a central portion movable between opposed positions at one side of the first pivot, said end portions pivotally engaging said second and third pivots, said pivots normally being out of alinement and arranged, when alined, to form an axis of maximum stress, and a contact carried by one of said end portions mounted to engage said stationary contact, said actuating means operable upon distortion by change in temperature to move said end portion of the tension member associated with the third pivot through said axis of maximum stress to move said movable contact by snap action between positions of engagement and disengagement with respect to said stationary contact.

3. In a snap acting switch, the combination of a molded open sided housing having a side wall and end walls defining a cavity, a removable cover enclosing said cavity. said side wall having a boss molded integral therewith to project into said cavity toward the cover, said boss having a groove formed thereon, spaced terminals mounted in said walls and projecting therethrough into said cavity, a contact in said housing shiitable between said spaced terminals, a resilient tension member supporting said contact and extending around one side of the boss, said tension member having its end portions movable between opposed positions and its central portion movable between opposed positions at one side of said boss, 9. compression member having one end pivotally supported in said groove and the opposite end pivotally engaged with said tension member adjacent the contact, a flexible member mounted in one wall of said housing and disposed in said cavity projecting past the boss on the side thereof away from the tension member and pivotally engaged with the latter member at the end thereof remote from the contact, said tension member, said compression member, and said flexible member forming a snap spring system having an axis of maximum stress and alternate positions of reduced stress, and means engageable with said flexible member for moving the end of the tension member engaged thereby from one position of reduced stress through said position of maximum stress to efiect movement of said contact between said terminals with a snap action.

4. In a snap acting switch, the combination of a housing having spaced walls defining a cavity, one of said walls having a boss projecting into said cavity toward an opposed wall, said boss having a groove formed thereon, one of said walls desaid end portion of the t n ion memb so- 75 fining a cover removable to permit access to the 5 cavity, spaced terminals mounted on said walls to project into said cavity, a snap acting spring system disposed in said cavity having an-axis of maximum stress and alternate positions of reduced stress, said system comprising a resilient tension member extending arcuately around one side of said boss having its ends movable between opposed positions and its central portion movable between opposed positions at one side a of the boss, a mobile contact on one end of said spring positioned to engage said terminals to define said opposed positions of said end, a rigid compression member having one end supported in said groove and the opposite end engaging said tension member adjacent the contact, a flexible member projecting through one of said walls into the cavity and engaging the end of the tension member opposite to the contact, said resilient tension member, said compression member and said flexible member being disposed in spaced, face to face relation, and means engaging said flexible member for shifting the end thereof in engagement with the tension member from one position of reduced stress through the axis of maximum stress to move said contact between said terminals with a snap action.

5. In a snap acting switch, the combination of spaced stops, one of said stops being formed by a fixed contact, a compression member having first and second ends, stationary means for mounting said first end to define a first pivotal connection, a resilient actuating member spaced to one side of said pivotal connection having a mounted end and an end free to move between opposed positions, a resilient tension member disposed on the opposite side of said first pivotal connection and extending therearound, said tension member having movable end portions and a central portion movable between opposed positions on said opposite side of said first pivotal connection, one of said end portions being pivotally connected with said second end of the compression member to define a second pivotal connection, a mobile contact carried on said one end portion of the tension member, the other of said end portions being pivotally connected with said free end of the actuating member to define a third pivotal connection, said members being stressed to define a snap spring system having an axis of unstable equilibrium defined by alinement of said pivotal connections and positions of reduced stress, and means for moving said actuating member to move said other end portion of the tension 6 member through the axis of unstable equilibrium to move said contact between the stops with a snap action.

6. In a snap acting switch, a housing of molded synthetic resinous material having walls defining a cavity, a boss integral with one of said walls extending into the cavity toward an opposite wall and having a groove formed thereon, said opposite wall being removable to permit access to the cavity, strip terminal members supported by said walls in edgewise relation to said one wall, one of said terminal members being flexibly resilient and another forming a stationary contact, a rigid strip compression member in edgewise relation to said one wall having first and second pivots, said first pivot being mounted in the groove for pivotal movement therein, said flexible terminal member having a third pivot associated therewith, said second and third pivots being disposed on opposite sides of said first pivot, a strip tension member in edgewise relation to said one wall extending around said first pivot, said tension member having opposite end portions movable between preselected positions and a central portion movable between opposed positions at one side of the first pivot, said end portions pivotally engaging said second and third pivots, said pivots normally being out of alinement and arranged, when alined, to define an axis of maximum stress, a contact carried on said tension member ad- Jacent said second pivot movable between preselected positions, one of which is defined by said stationary contact,.and means engageable with said flexible terminal member for moving the end of the tension member associated with the third pivot through the axis of maximum stress to move the contact by snap action between its preselected positions.

' OSCAR H. KAMINKY.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS 

